Orthogonal frequency-division multiplexing (OFDM) is a method for transmitting and receiving data from one device to another. In OFDM, digital data is encoded on multiple carrier frequencies and transmitted to a receiving device as a block of samples. More specifically, many modulated subcarrier signals are utilized to carry data on multiple parallel channels. Many applications may utilize OFDM. For example, power-line communications (PLC), wireless networks, long term evolution (LTE) communications all utilize OFDM.
One of the challenging aspects of OFDM communications is the presence of narrowband interferers in the channel. Narrowband interferers are unwanted signals that disrupt the reception of the data signal. Conventional systems may utilize windowing to mitigate the effect of narrowband interference (NBI) in multi-carrier modulation systems. Windowing consists of multiplying the time-domain of the transmitted signal by a window function prior to taking a fast Fourier transform (FFT). Multiplication in the time domain is equivalent to convolution in the frequency domain; therefore, the effect of windowing is to reduce the side-lobes produced by the interferer. The extent to which windowing can improve performance depends on the frequency of the interferer. If the interferer does not lie on one of the subcarrier frequencies, spectral leakage occurs, and the NBI affects all neighboring subcarriers.